Several suggestions have hitherto been made as to slow-releasing medical preparations from which a medicament contained therein is made to gradually release to maintain the efficacy of the medicament over a long period of time after they are administered to men or animals by adhering to their mucous membrane.
For instance, Japanese Laid-Open Pat. Publication No. 38412/76 (U.S. Pat. No. 4,059,686, patented Nov. 22, 1977) discloses a buccal preparation which is to be used by adhering to the buccal mucous membrane, being composed of a medicament, a sodium salt of polyacrylate, and an excipient (i.e., crystalline cellulose, mannitol, lactose, sorbitol, anhydrous calcium phosphate, amilose, etc.). Japanese Laid-Open Pat. Publication No. 130421/78 discloses a preparation for treatment of uterine cancer, to be used by adhering to the uterus mucous membrane, comprising hydroxypropyl cellulose, polyacrylic acid or its salt, and a carcino-static agent.
However, these slow-releasing preparations, when they are prepared in the form of a tablet, they have adhesiveness on both the upper surface and the reverse surface which presents some demerits, for instance, of making the handling inconvenient and often adhering to other place not desired at the time of administration. In order to lessen the touchy discomfort at the place where a slow-releasing preparation is adhered, it is preferable to make the preparation as thin as possible; however, there has been a problem that it is hardly possible to make the thickness of the conventional slow-releasing preparation less than about 1 mm from the viewpoint of mechanical strength.
The present inventors have come to complete this invention after having made a serious study with the object of developing an improved slow-releasing preparation to be used by adhering to the wet surface of mucous membrane, etc. to mend the faults found with the prior arts.